(1) Field of the Invention
The present invention relates to a fuel for a diesel engine. More particularly, the present invention relates to a fuel for a diesel engine, which comprises an alcohol, gas oil and castor oil in appropriately adjusted amounts.
In the instant specification and appended claims, by the term "gas oil" is meant a fraction distilled at about 200.degree. to about 360.degree. C. from petroleum, which also is called "diesel oil".
(2) Description of the Prior Art
An alcohol fuel has been considered as means for coping with expected exhaustion of petroleum or for preventing environmental pollution by exhaust gases. An alcohol is low in the vapor pressure and has a large heat of gasification, and since the cetane value of the alcohol is very low, the auto-ignition characteristic is poor and it is impossible to use such alcohol alone as a fuel for a diesel engine. Accordingly, there has been proposed a method in which an alcohol is used in combination with a conventional diesel engine fuel, for example, gas oil. However, the alcohol is hardly mixed with gas oil. For example, even if a completely anhydrous alcohol is used, when gas oil is added in an amount larger than 20% by volume at 10.degree. C., phase separation takes place and gas oil is not dissolved. This poor compatibility is conspicuous when the water content in the alcohol is high. Therefore, in view of a high affinity of the alcohol with water, this method can hardly be practically carried out.
An alcohol is hardly soluble in most of ordinary vegetable oils and mineral oils and only castor oil can be mentioned as a vegetable oil capable of dissolving alcohols therein. Accordingly, there has been proposed a method in which an alcohol is mixed with castor oil. However, since the viscosity of castor oil is high, it cannot be used in an amount exceeding 50%, and if the ratio of the alcohol is high, abnormal combustion occurs. Accordingly, such alcohol-caster oil mixture cannot be used as a fuel for a diesel engine.